21798636 has 12 divisors (see below), whose sum is σ = 50863512. Its totient is φ = 7266208.

The previous prime is 21798631. The next prime is 21798653. The reversal of 21798636 is 63689712.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21798631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 908265 + ... + 908288.

It is an arithmetic number, because the mean of its divisors is an integer number (4238626).

Almost surely, 2^21798636 is an apocalyptic number.

It is an amenable number.

21798636 is an abundant number, since it is smaller than the sum of its proper divisors (29064876).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21798636 is a wasteful number, since it uses less digits than its factorization.

21798636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1816560 (or 1816558 counting only the distinct ones).

The product of its digits is 108864, while the sum is 42.

The square root of 21798636 is about 4668.9009413351. The cubic root of 21798636 is about 279.3464177577.

The spelling of 21798636 in words is "twenty-one million, seven hundred ninety-eight thousand, six hundred thirty-six".